1. Field of the Invention
The present invention relates to a mobile unit such as a mobile phone provided with a fingerprint sensor that can easily be replaced when damaged.
2. Description of the Related Art
In recent years, mobile phones have spread and advanced remarkably. In addition to a simple telephoning function, the mobile phones have various functions, such as an electronic mail function, a personal-information storage, and an electronic payment. In association with such multiple functions, security needs to be ensured to prevent unauthorized use of a mobile phone and unauthorized leakage of information. Measures usually employed to ensure security are a system of previously registering a personal identification number (PIN) and allowing authorized use of a mobile phone only by entering the PIN.
The PIN system has some problems such that an entry operation may be troublesome and the PIN may be leaked. Therefore, recently, mobile phones with fingerprint sensor have been proposed, and such products have actually come into the market. In the mobile phones with fingerprint sensor, a fingerprint of its owner or an authorized user is previously registered in the fingerprint sensor, and use of the mobile phone is allowed if a fingerprint detected on it matches the fingerprint registered.
The structure of how to attach a fingerprint sensor to a conventional mobile phone is explained below with reference to FIG. 6 and FIG. 7. FIG. 6 is a vertical cross-section of a fingerprint sensor attachment portion in a conventional mobile phone. FIG. 7 is a perspective view of an internal configuration of the fingerprint sensor attachment portion. As shown in FIG. 6 and FIG. 7, a fingerprint sensor 200 is mounted on a predetermined location of a circuit board 202 by, for example, soldering. Various types of circuit components 201, including one that processes an output signal of the fingerprint sensor 200, are mounted on the circuit board 202. In these figures, reference numeral 203 represents operation keys such as dial keys, a * key, a # key, and a multifunction key; a plurality of key switches 205 corresponding to the operation keys are aligned on a key sheet 204, which is mounted on the circuit board 202; a key-side case 206 covers the whole of the circuit board 202, but the fingerprint sensor 200 and the operation keys 203 are exposed; and an underside case 207 is paired with the key-side case 206, for covering the whole of the underside. Furthermore, dust-proof rubber packing 209 is provided around an opening 208 of the key-side case 206 for exposing the fingerprint sensor 200.
The fingerprint sensor detects a fingerprint in such a manner that an operator's finger is made to contact the fingerprint sensor and is moved along the fingerprint sensor because of its function. Therefore, the fingerprint sensor is arranged at a location that is visible on an external area of a mobile phone and that can directly be touched with the finger. If the mobile phone needs to be fixed, and if dirt (darkening) and scratches appear on the fingerprint sensor, it is desirable to replace the fingerprint sensor to prevent degradation of the external appearance of the mobile unit and to ensure fingerprint detection capability of the fingerprint sensor.
However, in the conventional mobile phones, the fingerprint sensor 200 is mounted on the circuit board 202 by soldering, as shown in FIG. 6 and FIG. 7. Therefore, it is necessary to take the fingerprint sensor 200 off from the circuit board 202 by force, or to replace the whole of the circuit board 202 if required, and hence, the replacement of the fingerprint sensor 200 is quite troublesome.
Japanese Patent Application Laid-Open No. 2004-172467 and Japanese Patent Application Laid-Open No. 2004-006889 disclose examples of technology in which a fingerprint sensor is mounted on a specific board and the specific board is mounted on a circuit board such as a motherboard. In these examples, only the specific board needs to be replaced to replace the fingerprint sensor. However, because the specific board with the fingerprint sensor mounted thereon is mounted on the circuit board, some other circuit components cannot be mounted on a portion of the circuit board corresponding to the specific board. This restricts a mounting area, thereby affecting reduction of size of the whole device. If the mobile phone is dropped accidentally, the circuit board may be distorted due to drop impact. The fingerprint sensor in the above technology is a pin grid array (PGA), and is mounted simply on the circuit board via the specific board, and damage such as peeling off of solder balls may occur. Furthermore, there are some requirements, from the external design viewpoint, such that the fingerprint sensor be arranged in an outermost position, or in a rearmost position of an opening for exposure. However, in the case of the conventional structure in which the fingerprint sensor is mounted on the circuit board via the specific board, the position of the fingerprint sensor cannot be adjusted in the thickness direction of the mobile phone.